JAKARTA, Indonesia – Indonesian police said Friday a low-explosive homemade bomb caused a blast at a shopping mall southwest of the capital.

National police chief Gen. Badrodin Haiti said investigators are still trying to find the perpetrators and the motive for the bombing on Thursday. He said the bomb was made of materials that can be easily purchased.

The explosion in a restroom at the Alam Sutera mall in the Serpong region of Banten province, just outside Jakarta, caused no casualties.

It happened as authorities are preparing thousands of police and soldiers to safeguard the annual mass exodus of millions of Muslims coinciding with the end of the Islamic holy month of Ramadan.

Indonesia, the world's most populous Muslim nation, has a secular central government and has been battling terrorists since the Bali nightclubs bombings in 2002, which killed 202 people, mostly foreign tourists.

More recent terror attacks have been less deadly and have generally targeted security forces and local "infidels," not Westerners.